Lottery scratch-off or instant games have become a time-honored method of raising revenue for state and federal governments the world over. Indeed, the concept of hiding variable indicia information under a SOC has also been applied to numerous other products such as commercial contests, telephone card account numbers, gift cards, etc. The variable indicia are the letters, numbers, images or other indicia which determine whether a ticket is a winner typically by identically matching two or more of the particular letters, numbers, images or other indicia that are part of the variable indicia under the SOC. Literally, billions of scratch-off products are printed every year where the SOCs are used to ensure that the product has not been previously used, played, or modified.
Typically the variable indicia are printed using a specialized high-speed ink jet with a water-soluble dye imaged on top of display printed (e.g., flexographic, gravure, etc.) security layers that provide opacity, chemical barriers, and a higher contrast background for the ink jet variable indicia. The purpose is to ensure that the printed variable indicia cannot be read or decoded without first removing the associated SOC, thereby ensuring that a game or product is secure against picking out winners or extracting confidential information from unsold tickets or documents.
However, there are known methods (e.g., wicking, vapor, steam, alcohol soaks, etc.) for diffusing the ink jet variable indicia either through the substrate backing or the front SOC. When carefully applied, these methods can temporally reveal the previously hidden variable indicia, thereby enabling illicit people to determine if a given ticket is a winner or non-winner while leaving little or no trace and thereby only selling losing tickets to the public. The pick-out of winning variable indicia is made possible by a positive Signal-to-Noise (S/N) ratio of the diffused ink jet image through the substrate of SOC relative to the ticket's background ink noise.
In addition to diffusion, techniques have been developed for inducing fluorescence in the ink jet variable indicia dye. In these fluorescence attacks the dye is made to fluoresce with the ticket background not emitting any light or no light in the same wavelength as the fluorescing variable indicia ink jet image. Since the variable indicia emits fluorescent light in a wavelength different from the excitation source and the ticket background, there is a relatively high S/N ratio established between the fluorescence emissions of the variable indicia and the ticket's excitation light background. This relatively high S/N ratio allows for filtered (i.e., using a narrow band optical filter only allowing fluorescent wavelength light to pass) timed exposures with digital cameras that can successfully capture variable indicia images through an intact SOC that are not discernable by the human eye. This again allows for illicit pick-out of winning tickets with only losing tickets being sold to an unsuspecting public.
Similar to the above diffusion and fluorescence techniques, electrostatic charges have also been applied to instant tickets with intact SOCs creating a differential charge in the hidden ink jet variable indicia. At this point if an electrostatically sensitive powder (e.g., baby powder) is applied over the SOC, the powder will align in the two-dimensional shape of the (previously) hidden variable indicia yet again allowing for the underlying variable indicia to be viewed over an intact SOC and allowing winning tickets to be picked-out. When the charge is removed and the powder brushed away, no indication remains that the ticket's integrity was compromised. The electrostatic attack is based on establishing a positive S/N ratio of the ink jet variable indicia's charge relative to the ticket's background ink noise.
All of these variable indicia compromise practices have been mitigated with elaborate countermeasures meticulously developed in the instant ticket industry over decades. Most of these countermeasures rely on various printed (via a fixed plate—i.e., non-variable) chemical barriers to resist the aforementioned attacks. The general concept is to secure the variable ink jet indicia image and chemistry with the chemical barrier layer(s) reducing the variable indicia's S/N ratio to near unity or below relative to the ticket's background unless the SOC has been removed. However, these added barrier security layers have the disadvantage of added costs, reduced aesthetics, intermittent failures, as well as laborious testing and verification.
Additionally, there are known techniques for mechanically “lifting” the SOC and thereby viewing the variable indicia. The term “mechanical lift” refers to a process that uses a flat blade (e.g., X-Acto chisel blade #17) or other device to peel back a portion of the SOC to reveal previously hidden variable indicia. The lifted SOC is then glued back into place such that it is not obvious that the integrity of the coating has been breached. The industry has developed countermeasures to the previously described mechanical lift technique which involve changing the formulation of the SOC so that it is more difficult to remove and/or it flakes off or crumbles, rather than peeling off in one piece, thereby making “unassisted” SOC lifts more difficult. However, these techniques have done nothing to alleviate the vexing problem of “assisted” SOC lifts. Assisted lifts differ from unassisted lifts in that another medium or material is applied to the SOC (e.g., Krylon® acrylic clear spray) to strengthen it, thereby assisting anyone who is attempting a mechanical lift.
It is therefore highly desirable to develop techniques and methodologies for ensuring the security and integrity of scratch-off tickets and documents that is less reliant on chemical barrier technology attenuating the variable indicia's S/N ratio under special (i.e., predefined attack) circumstances, offering a more robust and generic defense. Ideally, these more generic defense mechanisms would also provide added security against mechanical SOC lifts, both unassisted and assisted. Particularly, these security techniques should enhance the aesthetics of the ticket or document rather than detracting from its appearance.